The development and maintenance of a deep water oil field typical requires many ROVs support to carry out a variety of different tasks. When exploration takes place under semi-hazardous conditions such as at deep depths ocean or at offshore locations, Remotely Operated Vehicles (ROVs) are typically used to gain access to the particular site or location. ROVs may be used for servicing vessels out at sea and for completion of a variety of different underwater tasks. These ROVs are typically self-propelled and usually include a variety of linkages to allow activities such as the retrieval, maintenance and repair of equipment to be accomplished. ROVs are also typically provided with video recording equipment and lighting to allow the controller of the ROV to better manipulate the ROV so that the ROV may accomplish its tasks underwater.
Out at sea, ROVs are frequently deployed using tether management systems (TMS). A tether management system may include a cage or a carriage for storing the ROV inside or it can be a top hat type carriage with the ROV stored below it. The carriage with the ROV is lowered from a surface vessel into the sea using either a conventional winch system or alternatively as an Autonomous Underwater Vehicle. When the carriage reaches the surface of the seabed, the ROV disengages from the carriage and is then directed by the controller to the work site. To facilitate the operation of the ROV underwater, the ROV is either tethered to the surface vessel via a long cable, or connected to the subsea umbilical assembly point or to a subsea power station or to a shore power source. Through this cable, the ROV will receive power and signals transmitted from the surface vessel to the ROV.
When the ROV is not in use, ROVs are retrieved back to the surface vessel and is usually stored within the carriage and on the deck of the surface vessel. This typically results in multiple launching and retrieval of the ROVs which are time consuming and risky. One of the problems associated with this arrangement is the limited deck space available to house the carriage and the ROV on-board the vessel. Due to the limited deck space available, it is common for surface vessel to have only one ROV with the carriage at any one point of time. However, the downside of having only a single ROV on-board is that in the event that the single ROV faces technical difficulties, the ROV may need to be replaced with a replacement ROV. This often causes significant delays before a replacement ROV can be brought on-board the surface vessel. In addition, an additional ROV on-board would also mean additional deck space is required to house the additional ROV or multiple surface vessels are to be deployed.
Many existing ROV deployment systems have a tether management system or carriage that can house only a single ROV. Although there are some systems which are able to house more than one ROVs, such systems are often bulky, inefficient and unsafe to use in bad weather and/or occupy significant deck space when stored on-board a surface vessel.
It is therefore desirable to provide a subsea ROV hub that seeks to address at least one of the problems described hereinabove, or at least to provide an alternative.